Why are pound and ounce abbreviated “lb.” and “oz.”?

Cecil replies:

You want part of the British system of weights and measures to make SENSE? Come on, it would ruin the whole effect.

“Lb.” stands for libra, the basic unit of Roman weight, from which our present-day pound derives. The libra weighed a little under 12 ounces avoirdupois.

“Oz.” stands for the Italian onza, ounce. It came into use in the 15th century. Ounce comes from the Latin uncia, a 12th, which is also the source of the term “inch.”

At one time there were 12 ounces to the pound, a usage that still survives in the system of troy weight used by jewelers and goldsmiths. Sixteen oz. to the lb. didn’t arrive on the scene until the 13th or 14th century.

Pound derives from the Latin pondo, “by weight.” You ask: why take pound from one Latin word but the abbreviation from a DIFFERENT Latin word? There is no rhyme or reason to it at all.

I know. Ain’t it beautiful?

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.